The present invention relates in general to protective cover devices suitable for precluding ingress of contaminants to the area of an inlet and/or an outlet valve mounted in the wall of a storage tank during periods of (i) use when the valve is open and coupled to an external liquid inlet and/or outlet conduit, and (ii) non-use when the valve is closed; and, more particulary, to a protective cover device of the foregoing character which provides an effective, reliable, dust-tight enclosure for the storage tank valve, especially in those environments wherein governmentally imposed and/or industry imposed regulations, or simply common prudence, mandate that protective measures be taken to insure that liquids can be safely introduced into and/or removed from a storage tank in a substantially contaminant-free environment--e.g., in an environment such as that encountered when on-loading and off-loading milk to and from a storage tank of a conventional dairy truck.
Currently, Federal regulations require that on-loading, transporting, and off-loading of various products, particularly those in liquid form--e.g., comestible products such as milk--be carried out in a controlled, essentially contaminant-free environment. Such regulations impose severe operating constraints when such liquid products are pumped into, transporated in, or pumped out of the transporting vehicle. Traditionally, milk is transported between the producing sites--viz., the dairy farm where dust and/or other airborne contaminants are commonly encountered--and a remotely located processing facility in a stainless steel tank trailer wherein the tank is provided with at least one milk entry and/or exit valve. In operation, liquid conduit means, commonly a hose having pump means operatively associated therewith, is attached to both the invidual producer's storage tank and to the tank trailer valve at each stop on a daily pick-up route, thereby enabling transfer of the milk in the producer's storage tank to the tank trailer for daily transport to the remotely located milk processing facility.
In order to prevent dust and other airborne materials from contaminating the valve, a dust cover has been conventionally placed about the valve and affixed to the milk tank trailer. Previously, such dust covers have taken the form of fabricated box-like enclosing members made of stainless steel or other metal affixed to the milk tank by suitable fasteners such as rivets or screws. Such box-like dust cover has been provided with one or more openings in the flat sides of the box, each covered by an access door, to permit access to the valve. In use, it is necessary to open the access door in the box-like cover, attach the hose, open the valve, reclose the valve when on-loading and/or off-loading is complete, remove the hose, and reclose the box-like access door. Because the hose to be attached to and removed from the valve is generally relatively rigid, tank truck operators have commonly experienced considerable difficulty in attempting to affix the hose to and/or remove the hose from the valve when the dust cover is in place. Moreover, difficulties have been encountered in obtaining an effective, reliable, dust-tight, and sanitary enclosure during periods when access doors are open to permit attachment of the hose, opening of the valve, conducting of an on-loading or off-loading operation, closure of the valve, and uncoupling of the hose from the valve.
During a normal operating day, a tank truck operator will normally be required to make a relatively large number of stops at individual dairy farms in order to collect the milk stored on a daily basis and transport the same to a suitable remotely located processing center. Usage of conventional box-like dust covers of the foregoing type tends to reduce the speed with which the tank truck operator can collect milk at each stop, thereby decreasing daily productivity. Moreover, such conventional fabricated box-like covers have proven difficult to clean on a routine, daily basis. Consequently, it has been a common practice employed by tank truck operators to simply not use the conventional dust covers, notwithstanding Federal and industry imposed regulations, thereby enabling the operator to significantly speed up the collection process.